DE4200237C2 - Enamel frits for sheet steel - Google Patents

Description

The present invention relates to special enamel frits for steel sheets.

For the enameling of sheet steel find both decarburized and non-decarburized Steels use either degreased, pickled and nickel-plated or only degreased and pickled or only degreased (Dietzel, Enameling, Springer-Verlag Berlin, Heidelberg, New York 1981, p. 185 ff.). The selection of the respective enamel frit Type depends on the steel grade and the degree of pretreatment of the steel grade (Petzold, Pöschmann, enamel and enamelling technique, VEB German publishing house for Basic Industry, Leipzig 1986, p. 78 ff).

Enamel frits which do not entail an adherence element (cobalt, nickel, antimony) To obtain good adhesion, they need a steel surface, which degreased, pickled and nickeled (Wratil, Mitt. Ver. Dtsch. Emailfachleute 16 [1968] 7-10). The stain activates the steel surface. The nickel plating acts as Adhesive between steel and enamel frit. Steels that are degreased and pickled, However, not nickel-plated, enamel frits require that at least one of adherence elements (cobalt, nickel, antimony) (Dietzel, Mitt. Ver. Dtsch. Email specialists 16 [1968], 55). If one uses these enamel frits at the same time for nickel-plated steels, we obtain in particular at the non-decalcified steels defective enamelling.  

In EP 02 84 934 A1 enamel frits are described on decarburized and non-decarburized steels which are only degreased, d. H. neither stained nor nickel-plated, produce defect-free and well-adhering enamels. As liable elements act cobalt and / or nickel. These frits are characterized by a high Content of boron. The amounts of silicon and titanium are about the same Amounts of boron and aluminum. The special atomic ratio causes this Email frits are very reactive. They assume the role of the pickling agent and activate the steel surface. However, you use these enamel fritters on Steel sheets activated by a stain or stain and nickel plating that is the result of an overreaction to erroneous ones Enamels.

In the same way behave enamel frits, the subject of EP 03 58 933 A are. Here, the aggressiveness towards unpickled steels is based on special ones Atomic ratios between cobalt, lithium and fluorine.

The task was therefore to provide enamel frits that had a well-adhering, flawless and visually uniform enameling on decarburized and non-decarburized Regardless of the degree of pretreatment of the steels (steels degreased and pickled and nickeled or only degreased and pickled or only degreased).

The problem could be solved with the enamel frit mixtures according to the invention the.

The invention relates to enamel frit mixtures which are characterized are that to 50 to 100 wt .-% of one or more fries of the Together A

SiO₂ 49.5-53.4% by weight TiO₂ 2.7-3.7% by weight ZrO₂ 0-0.2% by weight P₂O₅ 0-0.6% by weight B₂O₃ 13.4-15.7% by weight   Al₂O₃ 0.3-1.6% by weight Sb₂O₃ 0-0.3% by weight Fe₂O₃ 0.5-2.2% by weight BaO 0-6.0% by weight CaO 0.8-2.3% by weight MgO 0-0.2% by weight SrO 0-1.0% by weight ZnO 0-0.6% by weight CoO 0.7-2.1% by weight NiO 0.7-2.1% by weight MnO 1.5-4.1% by weight CuO 0.1-0.8% by weight Li₂O 2.0-3.0% by weight Na₂O 11.1-12.2% by weight K₂O 1.3-3.1% by weight F 0-2.4% by weight

and from 0 to 50% by weight of one or more frits of composition B

SiO₂ 24-63% by weight TiO₂ 0-15% by weight ZrO₂ 0-13% by weight B₂O₃ 3-22% by weight Al₂O₃ 0-12% by weight Sb₂O₃ 0-4% by weight Fe₂O₃ 0-4% by weight Cr₂O₃ 0-0.5% by weight BaO 0-19% by weight CaO 0-13% by weight MgO 0-2% by weight SrO 0-1% by weight ZnO 0-8% by weight CoO 0-2% by weight   NiO 0-4% by weight MnO 0-6% by weight CuO 0-3% by weight Li₂O 0-6% by weight Na₂O 6-23% by weight K₂O 0-5% by weight P₂O₅ 0-5% by weight F 0-8% by weight

in the frit or the frits of composition B
the sum of TiO ₂ and ZrO _{2 in} total between 2 and 17% by weight,
the sum of BaO and CaO total between 2 and 25 wt .-% and
the sum of Li ₂ O and K ₂ O in total between 1 and 8% by weight
should be
and the non-oxygen atoms in the frit or the frits having the composition B are to fulfill the following conditions:

[Σ (Li, Na, K) + 2Σ (Ba, Sr, Ca, Mg, Zn, Co, Ni, Mn, Cu) -ΣF-ΣP]: [Σ (B, Al, Sb, Fe, Cr) ] 1,1

and

[Σ (Si, Ti, Zr)]: [Σ (B, Al, Sb, Fe, Cr)] 1,1

where the sums are the sums of the atomic numbers of the respective ele is trading.

The enamel frit mixtures according to the invention allow error-free and optical uniform enamels with excellent adhesion to carbon-rich  (Normal) and low-carbon (OC) steels, regardless of whether the steels degreased and pickled and nickeled or only degreased and pickled or only degreased.

Both enamel frit mixtures containing 100% frits of composition A be as well as enamel frit mixtures made from frits of composition A and made of frits of composition B, give flawless enamels. On the other hand, enamel frits produce the same oxidic composition as the enamel frit mixtures according to the invention of frits of the composition A and B, but were melted in a frit from the raw materials, Enamels that have significant defects.

Enamel frits that are flawless enamels on any type of pretreated or provide non-pretreated steel, have the composition according to the invention A on. Surprisingly, it was also found that Emailfrittengemi from fritters of composition A and enamel fritters Composition B with the appropriate conditions, d. h., the due to the mixture are outside the composition A, as well as error-free Enamels on any type of pretreated or non-treated steel result.

Another advantage of the enamel frit mixtures according to the invention is that in the presence of up to 8 wt .-% spodumene (Li-Al-silicate) without disadvantages can be processed, which leads to enamelling, which is due to temperature change resistance (thermal shock resistance).

The Emailfrittengemische invention offer the Emailfrittenhersteller and the enamel fryer (enamelling) equally benefits.

The Emailfrittenhersteller must in the preparation of email recipes for the Enamelling of steel sheet an ever-increasing number of parameters be into account. This is due to altered steel qualities (transition from Block casting to continuous casting), different steel pretreatment (degreased, pickled  and nickeled or degreased and pickled or only degreased), design feature len steel body (flat or hollowware), different Emailauftragsverfah (powder-electrostatic dry application, classic wet application in Tauchverfah or with automatic sprayers, electro-immersion enamelling), energy-saving enamel ovens and enamels, to which higher demands are made variety of colors, layer thickness distribution, chemical resistance, crack resistance against temperature load (pyrolytic suitability) and temperature change Resistance to heat (thermal shock).

The respective application task now determines which of the displayed parameters must be linked together. For the creation of Recipes is a variety of enamel frits of various chemical To composition. The combination of enamel fritters has happened so far empirically, which meant that many enamel fritters due to Incompatibilities of frits with each other gave erroneous enamels. In contrast, the enamel frit mixtures according to the invention always ensure error-free enameling, what the effort to solve the respective apply training tasks considerably reduced.

Another advantage for the Emailfrittenhersteller is the application technology Width of the enamel frit mixtures according to the invention. For enamels with ver Similar property profile (eg crack resistance to temperature load) the creation of an enamel frit mixture according to the invention alone is sufficient Depending on whether the enameling factory degreases, ticks and nickel-plates the steels or only degreased and pickled or just degreased, regardless of whether the email lierwerk the powder electrostatic dry coating or the classic Naßauf in the dipping process or with automatic injection machines. This can be the bishe Tailored for the customers each customized, large enamel frittensimentiment become.

A major advantage for the enamelling plant is the high level of processing safety the enamel frit mixtures according to the invention, regardless of whether they are the Enamelling of flat or hollowware is. In addition, results for  Enamelling plants that subject their steels to intensive pre-treatment, d. H. Degrease, pickle and nickel, the chance, without affecting the current Enameling result on the nickel plating and on the stain of the steels verzich what the economic and ecological conditions in the enamel significantly improved.

The invention will be explained in more detail with reference to the following examples. The Weight data refer to weight percent, unless stated otherwise ben.

To calculate the conditions for the non-oxygen atoms, Ge percentages of oxidic constituents and of fluorine the ratio of Calculated non-oxygen atoms and the ratio indicated in such a way that the Sum of the non-oxygen atoms = 100%. The process is in Example 4 off specified in detail. The same procedure was followed in Examples 5 and 6.

For examples 1, 2 and 3 (according to the invention), enamel frits were taken together A made. They were made of commercially available enamel raw materials such as quartz flour, borax, alkali and alkaline earth carbonates, feldspar, titanium dioxide, alkali fluorosilazole katen and the corresponding heavy metal oxides at 1220 ° C "thread smooth" he Melted and quenched by water-cooled steel rollers.

The flakes thus obtained were electrostatically as a powder and as a slip through Spraying on substrates of decarburized (OC) and non-decarburized (normal) steel of 45 cm length, 6 cm width and 0.1 cm thickness applied and in a gradi oven baked in the temperature range of 750 to 900 ° C for 10 minutes. To assess the influence of steel sheet pretreatment were on the one hand Used substrates that were degreased, pickled and nickel-plated, and on the other hand Substrates without nickel plating and substrates without nickel plating and without stain.

For the powder application were in a porcelain ball mill 100 g Emailflakes and Grind 0.3 g of methyl hydrogen siloxane until the residue of the powder was less than 20 wt .-% on the 16 900 mesh (mesh size 40 microns).  

The powder, which had a surface resistance greater than 10¹³ ohms, was with an electrostatic gun under application of 70 kV voltage in one Quantity of 14 g (corresponding to 5.2 g / dm²) in a uniform layer on the steel substrate applied.

For the slip application, 1 kg of enamel flakes were used in a 3.5 kg heavy grinding machine balls-filled ball mill after the following mill offset to a slip ground:

Wt .-% Email flakes 100 silica flour 5 blue tone 4 boric acid 0.2 sodium nitrite 0.1 water 45 fineness 2-3% residue on 3600 mesh screen density 1.70-1.72 g / ml

From this slurry was so much on the steel substrates by spraying applied so that after drying and baking an enamel layer thickness of about 0.15 mm.

The enamel frits from Examples 1, 2 and 3 provided both powdered as also in the wet process on all steel substrates a perfect and optical unit Liche enamelling result.  

To assess the adhesion properties of the enamel frits of Examples 1, 2, and 3 was a liability test at the points of enamelling, in which the Baking temperature 790 ° C, 810 ° C, 830 ° C and 860 ° C. Corresponding DEZ leaflet F 6.2 the adhesion test was carried out with a striker under Ver Forming of the steel sheet carried out and evaluated. On all steel substrates was the adhesion above 810 ° C very good.

Furthermore, the enamel frits of Examples 1, 2 and 3 were in different Mixed proportions. An incompatibility was not observed tet. The combinations always gave faultless enamels with the above Liability profile.

In Examples 4, 5 and 6 (comparative), enamel frits of the composition B produced.

The frits of Examples 4, 5 and 6 were prepared in the same way as the fries of Examples 1, 2 and 3 applied. Unlike the frits 1, 2 and 3 showed the frits 4, 5 and 6 well-adherent, error-free and visually uniform enamels Only on the decarburized steels, which were degreased, pickled and nickel-plated. On The non-decalcified mild steel enamels were faulty. The fries 4 and 5 already had no adhesion to the non-nickel plated steel substrates, and Frit 6 finally already had on the steel substrates that neither plated nor nickel were pickled, no liability.

The frits of Examples 1, 2 and 3 were successively increased in proportion Enamel frits 4, 5 and 6 combined and the enamels in a known manner ago put and tested. The combinations in which the proportion of enamel fritters out Examples 4, 5 and 6 or mixtures thereof was not more than 50 wt .-% was (According to the invention), showed on all substrates, regardless of the grade of steel and the pre-treatment well-adhering, error-free and visually uniform Enamelsunun In the case of shares <50% by weight (comparison), no liability was attributed to sub straten, which were neither nickel-plated nor stained, present.  

In example 7 (comparison), another enamel frit is prepared and mixed with the frit th of Examples 1, 2 and 3 blended. Already a proportion of 10 wt .-% leads to very poor adhesion properties on the non-nickel plated steels. About that In addition, an incompatibility of the enamel frits with each other as a mistake adhesive enamel noticeable.

The enamel frit of Example 4 results in decarburized steel sheet degreased, ge and nickel-plated, an enamelling ge by cracking ge compared with voltage and temperature load, while the frits of the Examples 1, 2 and 3 show a variety of cracks.

The combinations of frits from Examples 1, 2 and 3 with the frit out Example 4 showed on all substrates regardless of the steel quality and Pretreatment crack-free enameling when the proportion of the frit of Example 4 between 20 and 50 wt .-% is.

To assess the crack resistance were elongated metal strips with the dimensions 225 × 60 × 1 mm enamelled 100 to 120 μm thick on both sides. The metal strips out Decarburized and non-decarburized steels were only degreased or degreased and pickled or degreased, pickled and nickel-plated. By pressing on both ends of a strip a deformation was generated in such a way that the strip center by 11 mm from the horizontal was deflected. In this position, each sheet metal strip was held at 400 ° C for 1 hour.

The frit of Example 5 provides acid-resistant enamels, with adhesion only can be achieved on nickel-plated steel substrates. Combinations of fries from the Examples 1, 2 and 3 with the frit 5 lead to acid-resistant enamels, which adhere well regardless of the degree of pretreatment of the substrates.

The acid resistance tests were carried out according to instructions DIN 51 150. The classification for decreasing acid resistance is made vi Suell. It takes place after 15 minutes exposure to a 10% solution of Citric acid in water at room temperature.  

The frit from Example 6 is characterized by good colorability with black and Brown color bodies. For visual assessment, the enamel frits of Bei games 1, 2, 3 and 6 each individually in the presence of different amounts (1, 2 and 3 wt .-%) of commercially available black and brown color bodies and ground Enamels made in a known manner. In frit 6 remained the color bodies during melting on the steel substrates intact, giving an intense Color development had the consequence. In the frits 1, 2 and 3 were the color bodies in the case of combinations of 1, 2 and 3 with 6 remained intact.

The frits of examples 1, 2 and 3 and the combinations of these frits with the Frits 4, 5 and 6 were added to spodumene (Li-Al silicate) prior to milling. The amount of spodumene was gradually increased by 1% by weight. It In all cases up to 8% by weight of spodumene could be added without the obtained enamels lost the property profiles described above. At contents above 4% by weight, the enamels showed a marked increase measure in the thermal shock resistance.

To evaluate the thermal shock resistance (thermal shock resistance) were non-nickeled and unpickled substrates (dimensions 100 × 100 × 1 mm) of decarburized steel coated on one side with so much powder that after Enamelling produced at 830 ° C. for 4 minutes was about 200 μm thick.

On the enameling applied lead was by means of a nonemail brought Bunsenbrenners located on the substrate side melted and the so heated substrate quenched in water: this process was as long as again picks up flakes were visible.

The enamels produced with spodumene-free frit powder showed in all Cases already after 1 to 2 cycles flaking. In the presence of Spodumene contents above 4% by weight were able to withstand 8 cycles be increased.  

In a further example 8, a frit 8 was calculated from a Mixture of 65 wt .-% of the frit of Example 1 and 35 wt .-% of the frit Example 4 is melted from the enamel raw materials and electrolytically as a powder static on steel sheet, which was neither pickled nor nickel-plated, applied. Both the adhesion and the crack resistance of the enameling were very bad.

In Example 9, a frit 9 was blended by mixing 65% by weight of the frit from Example 1 and 35 wt .-% of the frit of Example 4 and by subsequent Melting of the blend and made on steel sheet in the same way as Frit 8 applied. The adhesion and crack resistance of the enamel were bad.  

Example 4 (comparison)

Composition B

Σ (TiO₂ + ZrO₂) = 5.7% by weight
Σ (BaO + CaO) = 3.3% by weight
Σ (Li₂O + K₂O) = 6.1% by weight
Σ (Li, Na, K) + 2 Σ (Ba, Sr, Ca, Mg, Zn, Co, Ni, Mn, Cu) -ΣF-ΣP: Σ (B, Al, Sb, Fe, Cr)
36.39: 18.67 = 1.95
Σ (Si, Ti, Zr): Σ (B, Al, Sb, Fe, Cr)
46.41: 18.67 = 2.49

Example 5 (comparison)

Composition B

Σ (TiO₂ + ZrO₂) = 9.8 wt .-%
Σ (BaO + CaO) = 5.3% by weight
Σ (Li₂O + K₂O) = 2.3 wt .-%
Σ (Li, Na, K) + 2 Σ (Ba, Sr, Ca, Mg, Zn, Co, Ni, Mn, Cu) -ΣF-ΣP: Σ (B, Al, Sb, Fe, Cr)
31.35: 16.50 = 1.90
Σ (Si, Ti, Zr): Σ (B, Al, Sb, Fe, Cr)
45.82: 16.50 = 2.78

Example 6 (comparison)

Composition B

Σ (TiO₂ + ZrO₂) = 5.3% by weight
Σ (BaO + CaO) = 6.8 wt%
Σ (Li₂O + K₂O) = 3.1 wt .-%
Σ (Li, Na, K) + 2 Σ (Ba, Sr, Ca, Mg, Zn, Co, Ni, Mn, Cu) -ΣF-ΣP: Σ (B, Al, Sb, Fe, Cr)
27.01: 19.05 = 1.42
Σ (Si, Ti, Zr): Σ (B, Al, Sb, Fe, Cr)
46.09: 19.05 = 2.42

Example 7 (comparison)

Σ (TiO₂ + ZrO₂) = 7.6 wt .-%
Σ (BaO + CaO) = 1.4% by weight
Σ (Li₂O + K₂O) = 1.6 wt .-%
Σ (Li, Na, K) + 2 Σ (Ba, Sr, Ca, Mg, Zn, Co, Ni, Mn, Cu) -ΣF-ΣP: Σ (B, Al, Sb, Fe, Cr)
13.28: 17.16 = 0.77
Σ (Si, Ti, Zr): Σ (B, Al, Sb, Fe, Cr)
45.02: 17.16 = 2.62

Example 8 (comparison) (Wt .-%) SiO₂ 53.5 TiO₂ 2.8 ZrO₂ 1.0 B₂O₃ 13.4 Al₂O₃ 0.4 Sb₂O₃ 0.2 Fe₂O₃ 0.5 Cr₂O₃ 0.1 BaO 4.0 CaO 1.5 CoO 0.6 NiO 1.7 MnO 1.5 CuO 0.4 Li₂O 2.5 Na₂O 11.9 K₂O 2.2 F 1.8 @ Σ 100.0

Example 9 (comparison) (Wt .-%) Frit from Example 1 65 Frit from example 4 35 @ Σ 100

Claims (1)

Enamel frit mixtures for decarburized or non-decarburized, pretreated or untreated steels, characterized in that they contain from 50 to 100% by weight of one or more enamel frits of composition A SiO₂ 49.5-53.4% by weight TiO₂ 2.7-3.7% by weight ZrO₂ 0-0.2% by weight P₂O₅ 0-0.6% by weight B₂O₃ 13.4-15.7% by weight Al₂O₃ 0.3-1.6% by weight Sb₂O₃ 0-0.3% by weight Fe₂O₃ 0.5-2.2% by weight BaO 0-6.0% by weight CaO 0.8-2.3% by weight MgO 0-0.2% by weight SrO 0-1.0% by weight ZnO 0-0.6% by weight CoO 0.7-2.1% by weight NiO 0.7-2.1% by weight MnO 1.5-4.1% by weight CuO 0.1-0.8% by weight Li₂O 2.0-3.0% by weight Na₂O 11.1-12.2% by weight K₂O 1.3-3.1% by weight F 0-2.4% by weight and 0-50% by weight of one or more enamel frits of composition B SiO₂ 24-63% by weight TiO₂ 0-15% by weight ZrO₂ 0-13% by weight P₂O₅ 0-5% by weight B₂O₃ 3-22% by weight Al₂O₃ 0-12% by weight Sb₂O₃ 0-4% by weight Fe₂O₃ 0-4% by weight Cr₂O₃ 0-0.5% by weight BaO 0-19% by weight CaO 0-13% by weight MgO 0-2% by weight SrO 0-1% by weight ZnO 0-8% by weight CoO 0-2% by weight NiO 0-4% by weight MnO 0-6% by weight CuO 0-3% by weight Li₂O 0-6% by weight Na₂O 6-23% by weight K₂O 0-5% by weight F 0-8% by weight in the frit or the frits of composition B
the total of TiO₂ and ZrO₂ total between 2 and 17 wt .-%,
the sum of BaO and CaO total between 2 and 25 wt .-% and
the sum of Li₂O and K₂O in total between 1 and 8 wt .-%
and the non-oxygen atoms in the frit or frits of composition B satisfy the following conditions: [Σ (Li, Na, K) + 2Σ (Ba, Sr, Ca, Mg, Zn, Co, Ni, Mn, Cu). ΣF-ΣP]: [Σ (B, Al, Sb, Fe, Cr)] 1,1 and Σ (Si, Ti, Zr): Σ (B, Al, Sb, Fe, Cr) 1,1 where the sums are the sums of the atomic numbers of the respective elements.